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The most remarkable example of similar changes which I observed, was just above the junction of Ouerra Creek. The granite there exhibits most extraordinary conditions. The surface is decomposed, and the disintegrated materials have been deposited in waving layers concentric with the harder unaltered portions of granite upon them. A series of joints, defining the edges of the unaltered nodules of granite, pass through the re-deposited substance, and these joints are in part filled with furruginous matter, whilst at a little distance veins of limpid quartz, some of them twelve inches wide, cut through other parts of the decomposed granite, from south-west to north-east; the whole is covered by a thick deposit of pebbles of trap cemented by calcareous matter, which owes its origin to the decomposition of that rock. The quartz is of the same character as that in porphyry which I noticed at Eden in 1852.
Again, on one of the branches of Bella Creek flowing towards Ottley's Creek from the trap range between Gragin and Gurahmin, a thick deposit of white and red clay containing fine particles of quartz lies between porphyry and an amygdaloidal trap, which passes
into a variety very similar to that which occurs in Muswellbrook in the valley of the Hunter.
There are numerous other instances of change and position both in the porphyry and granite region, which prove unquestionably, that some of the trap rocks have issued out of granitic formation and overflowed it. I do not doubt, that, as in the instance noticed in King's Plains so in a variety of others, the porphyry as well as the granite had been decomposed superficially before the trappean outburst, and that in many cases the trap, as before mentioned in the neighbourhood of Boorolong (Report VI.), has flowed in ancient valleys of the older granitic period.
Hereafter I will produce evidence to show, that the period of the overflow was, at least further westward, posterior to the carboniferous formation, and that, therefore, it was, to a great degree, contemporaneous with the formation of the dykes and hills of trap which traverse the deposits of sandstone in the County of Cumberland.
Properly, the consideration of these rocks should have been deferred, but I have brought together the oldest and youngest of the formations hecause of their igneous character, and their frequent association.
The disintegration of the lofty masses of trap which form such pumerous peaks and flattopped ranges in the western quarters, and even immediately under the “ Dividing Range" of the eastern and western waters, has produced an enormous deposit of black or reddish brown mud in the flat-bottomed valleys amidst the mountains, especially along the Macintyre. It has served to fill up numerous hollows and basins which must once have been lagoons or swamps, and which in wet weather are still perfect sloughs. Mingled with this tenacious mud, which covers also so vast an area of the Liverpool Plains, are fragments and partly rolled pebbles of the harder rocks, which present themselves in half stratified deposits in the banks of many of the creeks, and which, as Swan Brook for instance, have cut their channels partly through them. In travelling from New England to the Gwydir, I passed over nearly sixty miles, most of them consecutive, of this black alluvial soil, and as it was wet from recent heavy rains I found it most unpleasant. But it is said to afford rich pasture, and therefore, stations are numerous upon it.
It has been before remarked, that calcareous concretions are common in this soil. The abundance of lime set free in the disintegration of the softer traps is the origin of these; and there must be an enormous amount of them, for they are collected by modern rains in hollows and channels and lie in heaps upon the slopes of many of the creeks, from the table land downwards to the flat interior.
I think it not improbable, however, that during the trappean outbreak calcareous matter may have been produced independently. It fell to the lot of myself and two gentlemen who joined my party, to pass
the night on one occasion in the bed of a creek, being the driest place we could find, near the head of Swan Brook. In the morning I found myself amidst a trappean deposit of a somewhat different kind to what I had before seen in New England.
The lower part of the banks were formed of hard nodular trap, jointed and apparently bedded ; over these was a deposit similar to what is called “volcanic ash” entangling nodules and patches of trap, the whole bound together by calcareous matter and covered by thin seams and layers of impure earthy lime, which also coated many of the pebbles. I counted thirty-two separate layers of this calcareous biscuit. It is not improbable, therefore, that the breaking up of such deposits may, in part, account for the small concretions of lime which strew the black alluvium. And again, the outburst of springs at the junction of trap with other formations may account for the deposit of calcareous tufa so common throughout this country, and which forms bars across creeks by cementing the loose blocks and shingle, and as I saw recently in a creek in the Bingera Gold Field, has invested the moss which covers the rocks and taken their impression, forming a similar tufa to those of Coton in Cambridgeshire, and of Harrowgate in Yorkshire.
That much of the trap has overflowed is seen by the thin tile-like clink stones which occasionally are met with. The amygdaloids are sometimes empty, but the cells of the vesicular portions are occasionally charged with crystals of chabazite and lime. I have seen but few instances of minerals of the zeolite family, which are common in the Illawarra district, but agates and chalcedony are ubiquitous in certain portions of the trap country, lying in numerous and singular forms upon the surface of the plains. . I have seen several which appear to have been collected around an organic form of probably marine vegeta
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tion, the agate appearing in radiating tube-like patches as if the silicia had been deposited upon some tough sea-weed. But it is difficult to conjecture, how the form could have been preserved in the hollow of a heated trappean paste or mud, so as to allow the subsequent infiltration upon it of the siliceous liquid.
I have not attempted to point out the separate localities where the trap rocks break out. These can only be shown upon a map, which cannot be coloured in the time at my command. I would, however, observe, that these rocks have broken out and assisted in forming the whole of the ribs from the backbone of the continent, sending offsets south and north, and limiting the basins of the waters flowing to the interior, the furthest rocks upon which, save those obscured by alluvium, are of hornblendic or felspathic trap, basalt, greenstone, or some form of porphyritic trap.
The auriferous country, of which I am next to make mention, is hemmed in by the granitic and porphyritic rocks before described, on the north-east; and on the west and south-west by the porphyritic and trappean ranges of Nundawar, the Gwydir or Drummond's Range, and the headlands that mark the embouchure of that river into the ocean. like interior, at Bareena (Gravesend), Tolunbar, and Ko-ungundarra, westward of Warialda ; eastward and north-eastward of these localities a long range in continuation of the separation between the waters of the Macintyre and Gwydir, from the neighbourhood of Cope's to Ottley's Creek, confronts the long series of cone-like peaks at the end of the Gwydir Range, by those of Balfour's Peak, and Carajin, the latter of which is the most elegant and graceful hill of the kind I have anywhere seen. It takes its name from its representing "a tall fellow,” which is also the meaning of Courada, the lofty summit which, amidst the more grotesque forins of Bounboorienbri, Terregee or Wohr Rock, Corya and Yalladurinda, presents itself in some aspects as a peak. Thus rocks, of igneous origin, form the furthest bulwarks of the mountain region against the intrusion of the winds which once blew over a waste of waters, but now range across a level region of alluvia supplied by the hills to the eastward.
It is impossible to avoid the conviction, that at one period the level interior must have been so occupied by waters. Seen from any of the points in advance to the westward, the perfect level of the horizon, high up, as is the ocean seen from a cliff, with the undulations of refractions in the atmosphere along the tops of the trees, just as waves are seen under similar influences, and with the estuary and bay, like forms of the flat land coming up to the bases and between the spurs of the hills, it requires but little imagination to fill in again these bays and open spaces with water, and to imagine such solitary hills as Bareena, in advance of the headland, as an island, since it is yet separated by the channel of the Gwydir from the range to which it belongs, and stands in the midst of the plain, as many an island on the shores of the present sea.
It is the influence of forces, which belongs to the province of geology to describe and apply, that has changed the face of Nature from what we conclude it once was, to what we behold it now; and viewed by the light which geology casts upon these mysterious works of nature, and looking forward to the progress of events which have already covered large tracts of this reclaimed bed of ocean, with flocks and herds and the habitations of civilized man, it is equally impossible to check the conviction, that before another century this vast region which was so difficult of access to its first explorer in 1832, may, by the aid of the iron in Australian hills, or the woods that clothe them, be traversed with ease from one coast to the other, and see even treasures, buried by alluvial floods below the soil, disentombed for the benefit of posterity.
With the facts before me it is not simple fancy which prompts this opinion. Whatever share the Karaula may have had (and that may have been but little, for reasons to be named hereafter,) in bringing down alluvial gold from the hills, the Gwydir las probably contributed no little auriferous detritus, and burying it beneath the accumulated sediment which it has deposited at the mouth of its estuary.
It is of this probability, and the facts connected with it, I have now to treat ; and in the following section, the metamorphic results of which I have produced but a few examples above, will be shewn to have been of a more important character in the period intermediate between the granitic and the carboniferous eras of slates and metamorphic rocks of the Bingera country.
From the preceding statements it would naturally be concluded that the north-eastern limit of the auriferous region stretching from the highlands of New England towards the north-westward is nearly along the Dividing Ranges, separating the waters of the Gwydir from those of the Macintyre. Such is very nearly the fact; for if a line be drawn from the head of Ollera Creek to the head of Ottley's Creek, a distance of 70 miles, on a bearing N. 45° W., little, if any, gold is found to the north-east of that line for many miles, and some gold will be found in almost every portion of the country to the southwest of it.
I am now to discuss that portion of the country which occurs north-westward of the granitic Gold Field of the upper part of the Gwydir and Namoi system, on which I have previously reported, and which is known by the name of the Bingera Gold Field.
The formations in this district repose in apparent regular order upon the gold-bearing rocks to the south-eastward ; they consist of slates, quartz rocks, jasperoid rocks, conglomerates, limestone, and flagstones, with bands of serpentine and diallage rock, the
laminæ directed chiefly from S. to N., or varying within limits of 20° to 30° on either side NEW of that normal trend.
SOUTH WALF.S. As slate rocks break out in the area between Turrabeile Creek and the Namoi, this slate country is evidently connected, geologically, with the Western Gold Fields, the junction being interrupted by the interference of the igneous chain of the Liverpool and Warrumbungle Ranges.
Looking then to this disposition of things, and the strike of the rocks, it is quite in accordance with the regular geological sequence to find the slate formation placed where it is found. The mean elevation of the country between the bends of the Namoi and Maule's Creek is about 1,000 feet above the sea, and the greater part of that area is nearly a dead level. The beds which I described as containing the casts of Lepidodendra, about the Peel, are found also at the head of the Manilla River, and those are succeeded in the ascending series by still younger carboniferous beds, of which I shall treat in the following section.
From beneath these lower grits and shales rise those formations which occupy the country between the gold-bearing granites of the Upper Gwydir and the Macintyre system. The height attained by them is from 2,000 to 2,800 feet above the sea, consequently, on the supposition, that they were once continuous upwards to the present level of goldproducing rocks of the same formation about the head of the Peel, there must have been a great denudation ; for without it the slope to the north-westward of a continuous plane would be, at least, 22 or 23 feet per mile, which the actual dip of the beds does not sanction, and, in any case, as the slate formation appears to mantle round the granite, a denudation over the latter formation, at least, is a necessary result.
The western side of this elevated country which, from the generally level surface in continuous spaces, has much the character of a table land, is bounded by the loftier trap and porphyritic clinkstone range of Mount Lindsay, having serpentine at its base between that range and the Rocky Creeks which flow from the Nundawar Range to the Horton River. In linear direction this boundary is about 60 miles in extent; it is, however, probably even more extensive, for serpentine is found in patches about the Bresi country, and is common in the drift of the Namoi.
At the head of Mywon or Myall Creek, where these formations commence on the eastern border, the breadth to the junction of the Horton and the Gwydir is about thirty miles. The eastern boundary is scarcely definable, because it inoculates with the western boundary of the granite Gold Field.
This area is not altogether in one block, for it is divided by the waters of the Horton, which flow in a valley, called by Mr. Cunningham, Wilmot's Valley, and by those of Bingera Creek, which flow in what the same traveller called Stoddart's valley. These creeks are about fifteen miles asunder, flowing nearly parallel to themselves and the meridian.
The field which is now worked as the Bingera Gold Field is eastward of Bingera Creek, and the chief researches have been made upon the high land between it, the Gwydir, and Keera Creek. Through this country there run to the Gwydir two creeks, Baro and Courongurra Creeks, both of which have supplied gold.
I may briefly describe this tract as occupied by a few slates of soft character, and a variety of metamorphic rocks of great hardness. The base seems to be a very hard siliceous greywacke conglomerate, and the originally softer rocks have been silicified and hardened into jaspers and flinty slates of precisely the same character as those which present themselves in the Hanging Rock district and on the Cockburn River. In the bed of the Gwydir I detected, amidst the river drift below Morulleroi, even fragments of other rocks of the same age, which I did not see in situ ; amongst these were hard unabraded regular-sided pieces of Goonoogognoo grit, and quartz pebbles filled with epidote. These must have been derived from beds like those at the head of the Peel. The west side of the gold tract is composed of a ridge of serpentine, varying through shades of green, and much contorted, in which are numerous veins of Picrolite, and of opaline meerschaum; lumps also of diallage rock occur between the lamina of the serpentine which are contorted around them.
This serpentine occurs in various parts of the Gold Field, and much of the gold has been extracted from its detritus, as it is on the “dry diggings” at Hanging Rock. The slates, when they are unaltered, are either brown or grey, seldom dark blue; they pass into flinty slate, jasper, and fibrous honestones. The latter occur on the middle part of Upper Bingera Creek, close to serpentine. The jaspers, as well as the softer rocks, are traversed by quartz veins, and by bands of quartz of considerable thickness; some of these still contain gold in matrix, and below them the metal may be procured from the surface. On one part of the Boro Creek the strike of the jasperoid rocks is about N. 10 E., dipping 20° to N. N. W., the cleavage plains dipping 70° to E. At the Commissioner's camp on Bingera Creek, the same rocks have a strike of nearly N. 20° W., dipping sensibly to eastward. In consequence of those deviations from the meridian, the hardness of the rocks and the convulsions to which they have been subjected, the country along these creeks is very broken, but the phenomena are on a small scale compared with those of the head of the Peel and its affluents. In the midst of the slates occur patches of grey limestone much water-worn and
superficially fluted, evidently very fossiliferous, but in such a condition as to leave only the
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most imperfect traces of encrinital stems, a few corals, and a turbo or allied shelli I could not find a single specimen capable of furnishing an idea of species, or of leading to identification of the age, but I doubt not, the rock is not younger than Devonian, and not older than the upper Silurian. I traced the slates and limestone, which is there but a little more perfeot, to the neighbourhood of Warialda, where also serpentine, entangling dialage rock, occurs close to the limestone which is altered by the contact.
In the lower ground of Stoddart's Valley, near the junction of Bingera Creek, the slates are soft and bedded with grits, like those of Brogalong in Maneero. Mywon or Myall Creek, which I descended to the junction with the Gwydir, flows throngh a country of similar formation, of grey and brown slates 'and' grits, with jasper and quartz; also intersected by parallel bands of serpentine running N. and S., and throwing off at Keriengobeldi, the slates and other rocks to N.E. and N.W. In one place, north of this, I found the slates much contorted, and dipping 38° — 42° to N.E., and in another serpentine slate dipping also 38° to N.W. On the northern part of Mywon Creek, there is abundance of trap, and I observed that the same phenomena which I noticed at Loondah (Salisbury) is exhibited there. The rocks altered by trap are covered by fragments and pebbles of the same, so as to present the appearance of a trap covered by conglomerate. So great is the analogy between one gold district and another.
The higher ranges eastward of Mywon Creek are clad with pines, and their contour and bare surfaces greatly resemble the limestone and siliceous ridges between Tamworth and Mowara Creek. I have little doubt they are of the same geological character, but I had not time to visit them.
To the westward the Myall Ranges, which terminate at the Gwydir, are steep and exhibit on the summit beds of sandstone, of which I shall make mention hereafter, and which also rests on the summit of the ranges between the Manilla and Cobbadah.
Between Bingera Creek and Warialda the spurs from the Mywon Range run to the westward. As I traversed them in a north direction, I traced the slates and other associated rocks breaking out in the banks of the water-courses, and gradually becoming covered on their lower extremities by the carboniferous formation.
The occurrence of serpentine, limestone, &c., near Warialda, in connexion with these indications, proves that the formations are continuous under the alluvial drift, which has covered all the low grounds throughout the region with innumerable fragments of quartz, iron, jasper, and other metamorphic rocks, the softer slates having gone in the formation of the soil. The accumulation of pebbles of these substances in all the creek-banks and in the river beds proves, how vast has been the destruction of the formations by denuding causes.
The continuation of these formations northwards cannot be doubted, however interrupted they may be by the intrusion of the porphyry and other igneous rocks on the Macintyre. At a place in the bed of that river between Cookanbaloòn dàn and Wapollawaa, I found an insulated patch of brittle and altered alumino-quartsoze rock, with broken and contorted laminæ, having a strike of N. 60° W., and a dip varying from 560 to 77o and 86° to the north-eastward. I believe this to indicate the ancient existence of the slate formation in that part of the country; it has since been destroyed by the agency of igneous forces and denudation. It occurred on the right bank of the river in the midst of black alluvium, and the river being in flood I could not examine beyond the locality. It lies about 12 miles E.N.E. from the head of Myall Creek. To the northward at Wallangra and near Ashbee's, about the 15lst meridian, limestone again breaks out, of the same character as that at Bingera and Warialda, with parallel bands upon the Mole, in the neighbourhood of slates and granite ; and on the heads of Macintyre Brook which are the northern sources of Dumaresq River, and to the westward of the extremely broken country at the back of Bolivia and Maryland, soft as well as compact slates, with the accompaniments of a gold country present themselves, showing by their appearance there that the granite is surrounded by a mantle of that formation.
Gold has been reported to me as having been found near Wallangra and at another place near by, (Gunyan on the Severn,) but I had no time to examine into the truth of the statement. A similar report was made to me respecting the head of Boomi Creek, which flows from a range between Ottley's Creek and Callandoon, and on which there is a conspicuous hill called "Blue Nobby, I am not inclined to think much gold could occur in such a country, except at a great depth below the surface; but eastward of this locality between the Karaula and the Dumaresq there is a bare tract, amidst the dense brigalo scrubs that are frequent in that country, which has induced some keen gold hunters to expect the metal there. The abundance of sandstone and trap in that vicinity forbids any hope of future profitable search. A bare tract is not generally a good indication of a gold field. I will shew another reason further on.
Without going beyond the limits of the present producing field on the Gwydir, I will now mention under what circumstances gold is found there.
It has already been long known that gold has been found near Barraba, Cobbadah as well as at Triabundie, and in various places in the Namoi country, as near Quierindie and Borah; not to multiply these, I will merely remark, that all the rocks from these localities and others further south, which I have examined, are in conformity with the indications about Bingera; the same serpentines, slates, and other rocks occasionally breaking out..
The extent of likely gold country on the Gwydir is therefore very considerable. And
NEW over all this, whether on the ranges, their slopes or side summits, or in the valleys, gold SOUTH WALES: seems to be scattered in the same general way ; not occurring as in the granite region in small and regular particles (except on the outskirts of the field, where I found by washing, some fine gold in inconsiderable creeks as well as between Bingera and Cobbadah, tuwards which I carried the same formations), but in water-worn irregular coarse lumps and rounded fragments of all sizes, which lie upon the surface or just beneath it, and are collected readily after rain by the kuife, which at Bingera is a common tool, in consequence of this facility and the difficulty of procuring water.
One piece of gold weighing twenty-six ounces without any admixture of other mineral matter was procured from a creek which had not been much excavated. This gold I saw. The vein from which it was derived must have been very considerable. I measured a piece of ground, excavated on the very surface, of the highest point of what are called á The Dry Diggings,” and found it be to 60 feet long, 7 feet wide, and 2 feet deep, in all 840 cubic feet. In twenty-seven days, three men took from this plot, only 2 feet deep, gold worth 8001. Other instances of good success were related to me on competent authority; so that this field must have presented to the first comers great inducements ; and I can readily understand that Mr. Commissioner Bligh did not misrepresent, according to such examples, the probable future value of the locality. I have myself seen persons pick up gold from the road side, in Stoddart's Valley, and I found gold myself, at but a little way below the surface. Gold has also been found on the range between the Horton and Bingera, on the range between the mouth of Bingera Creek and Gunerie, and in the alluvium of the Gwydir, near Morulleroi. It has also been found in Myall Creek, and in a variety of localities in the neighbourhood of the ranges on which the metal is collected.
Examining carefully into the geological features of the country, I was persuaded that all this gold was derived from veins of quartz, and that it must be of local origin. To say nothing of the improbability, that a lump of gold weighing 26 ounces would be carried by any such streams as now exist, under the present conditions of position and dryness of the climate and soil, to a great distance, and it clearly could not come from the higher granite country of the Rocky River, or any part of that region, where the gold is fine, it is not worth conjecturing whether it could have been brought down from the Hanging Rock country, though the similitude of the gold found in the two fields is very great.
Taking into account the physical circumstances of the country, I cannot but conclude, that either an extensive denudation of gold producing rocks which once covered the goldgranite of the upper Gwydir country, has left its spoils upon the lower levels of Bingera, and its neighbourhood, or that a similar denudation of higher beds of that formation, now strewn with gold, must have taken place; and, since we find that the vein of quartz yet existing carry gold in them, and many of the fragments of gold are still sprinkled with relics of quartz, the conclusion necessarily is, that this Bingera country was once far richer than now, and that there is every probability that formerly a gold region extended, with few interruptions, from the Macquarie Basin to the Darling Downs, of which the principal remaining portions are the country along the Namoi and Gwydir, and that about the heads of the Condamine and the Dumaresq Rivers, and Macintyre Brook, where there is an extensive development of slates resting upon the higher granite country of Maryland, and in the creeks which traverse them there is gold.
But, if this conclusion be adopted, it will occur to one to consider whether there must not be many spots yet untried which will repay labour, and whether in a region where the detrital accumulations are so enormous, that wells from 70 to 90 and 140 feet have been dug through them, along the Gwydir, without reaching water, and where consequently the drift from the mountains must have been filling in the old cavities of the far west for ages, there must now of necessity be some gold, however deep, buried beneath it, from the wear and of the dry land which has evidently, by the action of the ocean itself, during oscillations of the submarine platform and the atmospheric agencies during long ages, converted a watery waste into an abode for man.
The only reply to these deductions should be the extensive use of the boring rod, which is the only instrument that could detect their value, or show that they are chimerical
. In the mean time, I think that the Bingera Field has not been fairly tried, and that a laborious population is required there. No one can find gold where it does not exist, but no one can obtain it sl.ccessfully who prefers repose to toil
, and who thinks it of use only to gratify evil indulgences. That metals exist in this Gold Field, in more abundance than is supposed, is rendered probable by the abundance of iron which occurs there, by the existence of veins of carbonate of copper, and by the presence of tellurium, which is sometimes frequent in the gold washing, I believe it has been mistaken for rhodium, but this last named metal has, in some instances, the regular hexagonal form, and cannot be mistaken readily for that scarce and probably seldom simple metal, rhodium.
I cannot take leare of this field without acknowledging the courteous and kind attention of Mr. Commissioner Bligh, who accompanied me to the several localities, and offered me every assistance and information in his power, during my stay on the Gwydir; and I deem it only an act of honesty to express my opinion, that he did not deserve some of the comments that were made on his early Reports.
I wilfonly add to this section, that copper and lead are both distributed in other portions of the western falls of New England, that the former occurs on the Manilla waters, near